Heretofore, as a diagnostic detector detecting radiation, particularly X-ray, an X-ray image detector based on active matrix has received remarkable attention. By exposing the X-ray to a planar detector, an X-ray radiograph or a real-time X-ray image is outputted as a digital signal. Because of a solid detector, expectation is particularly large in image quality and stability as well. For this reason, a lot of universities and manufactures have undertaken research.
In initial practical realization, the detector collecting still image with relatively high radiation has been developed for generally radiographing chest, and recently has been commercialized. By clearing a higher technical hurdle, application is progressed toward commercialization for a field of circulatory organs or digestive organs. In the field, a real-time moving image is necessary to be realized with 30 frames or more per second under fluoroscopic radiation. In the future, important development items are not only a conventional X-ray image detector limiting the installation site as a detection system but also a portable X-ray detector allowing X-ray image diagnosis at any place where the diagnosis is needed and a product allowing auxiliary radiographing of the X-ray image detector in a fixed detection system.
A radiation detection device detecting radiation, particularly X-ray, is used in a wide field such as non-destructive inspection, medical diagnosis and chemical research of structure analysis or the like.
While there are radiation detection devices, a radiation detection device including a radiation detection panel is well known as a high-definition device having high sensitivity, the radiation panel having an optical detector on which a fluorescent material layer converting radiation to light is directly formed. The photodetector includes a photoelectric conversion element unit that a plurality of photosensors and a plurality of TFT (Thin Film Transistor) as switching elements are disposed. The switching element in each pixel is connected to a gate line as a row and a signal line as a column. The gate line and the signal line are disposed in a lattice pattern, and connected to each pixel disposed in the lattice pattern.
By stacking fluorescent material converting X-ray to visible light on a planar photodetector, the incident X-ray from the outside is converted to the visible light inside the fluorescent material and the generated visible light is incident on the planar photodetector. At this time, the incident visible light is converted to a charge in a photodiode inside the planar photodetector. This charge is stored inside the photodiode or inside a capacitance element connected in parallel.
X-ray image information converted to a charge is transmitted outside the substrate through the switching element (TFT) connected to the photodiode. The TFT connected to the gate line having the potential changed becomes the conduction state through the change of the gate line potential. The stored charge in the photodiode connected to the TFT which becomes the conduction state or inside the capacitance element is output to the outside through the TFT. The charge output to the outside is output to the outside of the glass substrate through the signal line connected to the TFT.
The charge signal output to the outside of the glass substrate is input to an integrating amplifier connected to each signal line. The charge information input to the integrating amplifier is converted to a potential signal to be output. The potential signal output from the integrating amplifier is converted to a digital value by an analog/digital converter and finally compiled as an image signal to be output to the outside of the X-ray image detector. The radiation detection panel is supported on one face of a plate-like support plate and a circuit board driving the radiation detection panel is supported on another face of the support panel. These radiation detection panel and the circuit board are electrically connected on a flexible circuit board.
By combining a metal and a resin component so that the support plate supporting the radiation detection panel and the circuit board connected to the radiation detection panel are protected from the outside and become together, a chassis of the radiation detection device is constituted. In particular, in the portable X-ray image detector, a thin type/light weight is achieved, and replacement with a film medium incorporated into the conventional cassette and radiographing the X-ray image is made.